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Nutrient loads enter the lower Truckee River of western Nevada, affecting the growth of attached algae (periphyton) which causes depressed nighttime dissolved oxygen (DO) levels. The lower Truckee River is home to the endangered cui-ui and threatened Lahontan cut-throat trout, with DO standards being established to in part protect these species. Hydrodynamics, nutrient concentrations, periphyton biomass, and DO data spanning August 2000–December 2001 were used to calibrate and verify a modified version of the Water Quality Analysis Simulation Program Version 5 (WASP5). Under typical loading conditions the periphyton community is nitrogen limited, however nitrogen loading from an upstream wastewater treatment facility increased greatly during the analysis period due to approved site construction activities (discharge permit excursion) causing the periphyton community to temporarily become phosphorus limited. The developed modeling approach, with limited calibration, was able to accurately track dynamic sys...

Sea ice communities were sampled across the Ross Sea in the austral autumn. The biota in first-year pack ice was assessed by measuring chlorophyll a (chl a), phaeopigments, total particu- late carbon and nitrogen (POC and PON, respectively) and collecting samples for identification by microscopy. Physical and chemical parameters were also measured to characterize the environ- ment. Chl a concentrations in ice ranged from 0 to 96.9 µg l -1 in discrete samples and from 0.02 to 20.9 mg m -2 for values integrated throughout floes. Maximum values were similar to those observed in first-year pack ice at other Antarctic locations. Chl a concentrations varied with ice structure and with latitude. POC:chl a and C:N ratios (molar) were high, possibly indicating detritus accumulations. The higher chl a levels north of approximately 72° S were apparently a result of ice forming in the south early in the season with subsequent advection to the north. These dynamics would result in older ice in the mid- or northern pack ice zone that was maintained in a favorable light and temper- ature regime during the seasonal progression of formation and drift. Chlorophyll levels were low in surface-layer communities. High chlorophyll concentrations were associated with internal communi- ties. Bottom-layer algal populations, while present, did not reach the levels of high biomass reported for autumn blooms in some land-fast ice regions. Apparent nutrient and CO2 depletion were corre- lated with biomass parameters but accounted qualitatively for only a fraction of the biomass accumu- lation measured. Overall, autumn ice-associated production in the Ross Sea may be lower than expected because of the ice drift dynamics, apparently low production in the near-surface layers of first year ice flows, and the absence of rich bottom-layer assemblages.

Lake Vida, located in Victoria Valley, is one of the largest lakes in the McMurdo Dry Valleys. Unlike other lakes in the region, the surface ice extends at least 27 m, which has created an extreme and unique habitat by isolating a liquid-brine with salinity of 195 g L−1. Below 21 m, the ice is marked by well-sorted sand layers up to 20 cm thick, within a matrix of salty ice. From ice chemistry, isotopic abundances of 18O and 2H, ground penetrating radar profiles, and mineralogy, we conclude that the entire 27 m of ice formed from surface runoff, and the sediment layers represent the accumulation of fluvial and aeolian deposits. Radiocarbon and optically stimulated luminescence dating limit the maximum age of the lower ice to 6300 14C yr BP. As the ice cover ablated downwards during periods of low surface inflow, progressive accumulation of sediment layers insulated and preserved the ice and brine beneath; analogous to the processes that preserve shallow ground ice. The repetition of these sediment layers reveals climatic variability in Victoria Valley during the mid- to late Holocene. Lake Vida is an excellent Mars analog for understanding the preservation of subsurface brine, ice and sediment in a cold desert environment.

Rock, soil, and ice penetration by coring, drilling or abrading is of great importance to a large number of space and earth applications. Proven techniques to sample Mars subsurface will be critical for future NASA astrobiology missions that will search for records of past and present life on the planet. An Ultrasonic/Sonic Drill/Corer (USDC) has been developed as an adaptable tool for many of these applications [Bar-Cohen et al., 2001]. The USDC uses a novel drive mechanism to transform the ultrasonic or sonic vibrations of the tip of a horn into a sonic hammering of a drill bit through an intermediate free-flying mass. The USDC design was modified to fabricate an Ultrasonic/Sonic Ice Gopher that is designed to core down to meters depth for in situ analysis and sample collection. This technology was demonstrated at Lake Vida in the Dry Valleys, Antarctica. Coring ice at -20°C as in Lake Vida has been a challenge and efforts were made to develop the required ice core cutting, ice chip handling and potential ice melting (and refreezing) during drilling. The analysis and fabrication challenges and testing results are presented in this paper.

There is growing evidence for ice and fluids near the surface of Mars with potential discharge of brines, which may preserve a record of past life on the planet. Proven techniques to sample Mars subsurface will be critical for future NASA astrobiology missions that will search for such records.